1. Technical Field
This invention relates to an apparatus and method for measuring a supporting force of large diameter ferroconcrete piles installed at a scene by means of a bi-directional front end oil pressure loading apparatus using a high pressure loading system capable of measuring supporting force, sinking amount, and axis load distribution on ferroconcrete piles installed at the scene, the ferroconcrete piles being used as base piles in the fields of public engineering and the construction industry.
2. Related Art
In a method for determining the vertically limited supporting force of piles, the following are employed: a static post loading test, a static and dynamic loading test, a dynamic loading test, a static mechanical supporting force formula, an experience formula such as a scene test result, a wave equation, an assumption like a post analysis code, and an assumption like a continuous body analysis. High reliance is placed on the static post loading test.
The static post loading test is a generic form of testing, and is used when upper architecture is constructed with the application of a real load to a post. Thus, it has a high degree of reliability.
In the above described static post loading test, however, methods of establishing pressurization and a reaction system and a spacious test lot are required for the purpose of applying a load, resulting in many requirements such as air conditioning, maintenance of the condition of the scene, and the like.
In addition, if the supporting force is smaller than a required value due to an operational defect because a load to be imposed on one post is very heavy, the entire construction can be adversely affected in view of utility and stability of a large diameter post.
Furthermore, ground is excavated at the scene, and then concrete is poured into the excavation and recuperated. This recuperation causes the supporting force of a post installed at the scene to be able to be largely changed, depending on departures from working procedures or an undesirable change in ground condition.
Therefore, it is impossible for a designer to avoid implementing a conservative layout when a load is used and laid out with its value assumed and tolerated on the basis of ground conditions, thereby amounting to a considerable consumption of a natural resource.
To solve the above described problems, U.S. Pat. No. 5,576,494 discloses an apparatus for measuring a supporting load using an Osterberg cell, in which a high oil pressure jack is installed in a post, and a reaction against the application of a load by a front end supporting force and a main abrasion generated from loading is produced. As a result, there is no requirement for a static post loading test or for separate load applying apparatus and reaction equipment, resulting in the ability to operate in a narrow test space or at a tilted location.
Such a supporting load apparatus using an Osterberg cell, as described in U.S. Pat. No. 5,576,494, was developed in the 1980's, and comprises flat upper and lower discs, a cylinder having a piston contacting the bottom of the flat upper disc and a body contacting the top of the flat lower disc, a connection member coupled to the upper and lower discs by welding both ends to the bottom of the upper disc and the top of the lower disc, respectively, and a displacement unit for measuring a displacement of the upper and lower discs.
In such an apparatus for measuring a supporting load using an Osterberg cell, substrate concrete to be poured to the bottom is recuperated so that the substrate concrete may have a rigidity stronger than a predetermined value before an Osterberg cell is safely received, and more concrete is poured so that concrete piles are formed after the completion of the safe receipt of the Osterberg cell. As a result, it takes a long time to measure a supporting load.
Although the substrate concrete and the additional concrete are the same in view of their materials, they have a different solidity because their pouring times and recuperating times are different.
Accordingly, concrete piles to be used in a laboratory experiment are different from those used in a working environment in view of front end supporting force and column face abrasion, which results in a problem in terms of degraded reliability in such an apparatus for measuring a supporting load using an Osterberg cell.
In addition, such an apparatus for measuring a supporting load using an Osterberg cell has a flaw in that only a load for supporting non-iron concrete piles can be measured, whereas the concrete piles utilized at a working scene are concrete piles with iron built in.
To solve the disadvantages contained in U.S. Pat. No. 5,576,494, Korean Patent Laid-Open Publication No. 10-2005-0002682 discloses an apparatus for measuring a supporting load which comprises upper and lower discs, a cylinder coupled between the discs, a front end force measuring instrument including a displacement measuring rod for measuring displacement of the discs, iron elements coupled to the top of the front end force measuring instrument, and an axis load transition measuring instrument for measuring ground abrasion with coupling to the iron elements.
Such an apparatus for measuring a supporting load has deficiency in that the size of basis piles is limited and the number of oil pressure cylinders is unlimited, with the result that such an apparatus is not adopted for a necessary loading capacity.
In addition, the increased number of oil pressure cylinders makes it difficult to equally adjust oil amount, and therefore it is difficult to accurately adjust a load to be tested.